If you see too many target countries in Google Merchant Center, you do not want to target them. Then there are two areas to check.
Go to Google Merchant Center > Products > Feeds > Click on your Feed > Settings > and remove any additional countries that are enabled. You can do this by clicking on the pencil icon next to the countries.
Go to Google Merchant Center > top right corner > click on the wrench icon > shipping settings
Here remove any shipping settings for countries you do not want to target by checking the box next to the shipping setting and clicking on the bin icon.